<?php
$books = array(
	       "red" => "red book",
	       "green" => "green book",
	       "blue" => "blue book",
	       "other" => "yellow book"
	       );
echo $books["red"];
// 这种调用不规范，但是仍然会输出blue book
echo $books[other], "<br>";

define("other", "green");
// 现在other的输出和上面other的输出值不同了,因为这里做了定义:)
// define只能是标量，不能对象或者数组之类的。
echo $books[other], "<br>";
echo $books["other"];

$x=1;
$x++;
echo $x, "<br>";
?>